There is now increased competition among motor-vehicle manufactures ______ has resulted in better cars at lower prices.
 
【正确答案】 C
【答案解析】 本题考查定语从句。根据从句中的谓语动词has确定先行词为increased competition,从句中缺少主语,故选关系代词that,所以C项为正确答案。